The Syntactic Category Rule

Why We Mix Up 'Osama' and 'Obama': A Linguistic Reason (The Atlantic)

The syntactic category rule means that when two words are confused for one another the "target" (the word replaced) and the substituting word are almost always of the same syntactic category. In normal speak: nouns replace nouns, verbs replace verbs, and so on. If "Obama" were a verb instead of a noun... we would be substantially less likely to confuse it with the noun "Osama."